Stroke ranks second after ischemic heart diseases as cause of lost disability-adjusted life-years in high-incomes countries and as cause of death worldwide (Lopez et al., Lancet 2006; 367:1747-57).
Different clinical pictures summarized under the term “stroke”, which term describe a disturbance in the blood supply to the brain. This can be due to ischemia (lack of blood supply) caused by thrombosis or embolism or due to a hemorrhage.
An ischemia insult results in damages to tissues or organs in the affected area as a result from a cascade of events from energy depletion to cell death. Intermediate factors include an excess of extracellular excitatory amino acids, free radical formation and inflammation. Immediately after arterial occlusion, a central core of very low perfusion is surrounded by an area of dysfunction caused by metabolic and inonic disturbances, but in which structural integrity is preserved. In the first minutes to hours the clinical deficits do not necessary result in irreversible damage. It is therefore of outmost importance to reduce the time wherein the tissues receive low perfusion.
Approved therapeutic approaches to treat arterial thrombosis, such as a cerebral stroke, use plasminogen activators alone or in combination with antiplatelet drugs and anticoagulants.
Approved plasminogen activators currently used in acute ischemic stroke include only tissue-type plasminogen activator (“tPa”). Administration of tPa in the setting of occlusive thrombus enhances the rate of fibrin degradation, restoring arterial patency and blood flow to ischemic tissues.
Plasminogen activators are enzymes that activate the zymogen plasminogen to generate the serine proteinase plasmin, which degrades fibrin.
Tissue-type plasminogen activator is a fibrin specific activator of plasminogen and an effective thrombolytic agent, which primary application is in the clinic for the treatment of heart attack and stroke.
Natural tissue-type plasminogen has a plasma half-life of about six minutes or less. Due to its rapid clearance from the circulation, tPa is usually infused to achieve thrombolysis. Front loaded dosing with increased concentrations of tPa has shown more rapid and complete lysis compared to the standard infusion protocol and early potency is correlated with improved survival rate.
tPa is commercially marketed as recombinant alteplase (under tradename such as Actilyse® or Activase®) by Boehringer Ingelheim. In USA FDA has approved a dose of 0.9 mg/kg with a maximum of 90 mg in acute ischemic stroke. Activase® is administered as infusion over 60 minutes with 10% of the total dose administered as an initial intravenous bolus dose over 1 minute.
The treatment should be initiated within 3 hours after onset of stroke symptoms. However recent data prolongs this period to 4.5 hours since onset of stroke symptoms. The reason for this time restriction is due to an increasing occurrence of side effects, most notably intracranial hemorrhage, which has constrained its clinical use.
Another suggested strategy to treat acute ischemic stroke has been to administer erythropoietin (EPO), because EPO has been shown to have both neuroprotective and neurogenerative effects. However, in a recent clinical study in the treatment of acute ischemic stroke it was shown that patients receiving both erythropoietin (EPO) and tPa had an increased mortality (Hannelore et al., 2009; published online by Stroke, October 2009). This finding was somewhat unexpected because it was believed that a beneficial effect could result from combining tPa (due to its clot-dissolving propertied) and EPO (which would salvage potentially viable brain tissue). However, the clinical trial showed that a combination of EPO and tPa was not advantageous.
A new drug under the development for acute ischemic stroke is carbamylated erythropoietin (CEPO). It is chemically modified EPO by carbamylation of lysine residues (Leist et al. Science. 2004; 305(5681):239-42 hereby incorporated by reference in its entirety) which has the advantage of not binding to the erythropoietin receptor and is thereby without haematopoietic side effects. Despite the lack of binding to the erythropoietin receptor, CEPO retains full cytoprotective properties, demonstrating that CEPO mediates its beneficial effects via a mechanism different from that of the classical erythropoietin receptor.
In the present application, it has been confirmed that EPO, tPa and the combination of EPO and tPa treatment increased the intracranial bleeding compared to saline injections. Surprisingly, however, the inventors found a combined treatment with tPa and CEPO in a stroke model reduced cerebral hemorrage.
The object of the present invention is therefore to provide an improved treatment regime which reduces the haemorrhaging while at the same time effectively lysis the clot and re-establish perfusion to the affected areas.